Study of crystallization and morphology of ammonium diuranate and uranium oxide

Ammonium diuranate (ADU) and its heating product uranium oxides (UO3 + U3O8) are important intermediates for nuclear fuel production. The microstructure and particle size distribution (PSD) of ADU powder produced at various stages of precipitation have been measured to study the particle growth of ADU. The change of morphology of ADU and UO3 + U3O8 has also been studied when gaseous ammonia is added instead of aqueous ammonia solution and when a seeding agent is added to the uranyl nitrate solution before precipitate formation. It has been observed that the ADU particles form basically agglomerates of submicron platelets. The microstructure of ADU was retained in UO3 + U3O8 even after calcination.